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PCA9555DBQR Randomly latch up during power on. I2C SDA line stuck low.

Randy Fung
Prodigy 60 points
Other Parts Discussed in Thread: TCA9555

Dear Support, 

We are using 4 x PCA9555DBQR on our  design and about to release to production. We are seeing some strange behavior on this I2C expander chip.

When we power on,  the SDA (pin 23) stuck low and hold our I2C bus access. Some of the board work and some don't. We tried to slow down the power 3.3V rails by adding 100uF cap. It seems to fix the problem on one board. But when we applied the 100uF cap to another board. It did on seem to work.

I noticed there are quite a few complains on this chip. And people are designing out of this chip. 

I noticed the SDA line is controlled by a transistor to ground by inter block.

What is the problem and how can we fix this issue as we about to release this PCBA to production?

I also found another similar part. TCA9555. Is this suppose to be the replacement?

Can you please advise?

Thank you.

Randy